is required to be performed monthly for 30 minutes at either 30% of rated load or at loads to maintain the minimum exhaust gas temperatures set by the manufacturer.
WHITE PAPER
Figure 4
Annual Fuel Consumption
2500
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Up to 71% reduction in fuel consumed for exercise and maintenance in a single year
1500
1000
Month 12 represents the NFPA 110 annual full-load testing of the generator set
500
0
0
2
4
6
8
10
12
Months
Monthly Loaded
Monthly No Load
Every Four Months No Load
Figure 4
Revising Maintenance Schedules Rehlko Service Providers Will Advise
maintenance schedules and significantly reduce the once-monthly load-banking requirements. In fact, test and field experience with generators such as the Rehlko KD Series suggests that unloaded monthly exercise is allowable, as long as the generator is load bank-tested annually, which is standard practice for most operators. Switching to Annual Load Testing The savings from switching from monthly to annual loaded testing are compelling. For example, a 3250-kilowatt running a load-banking cycle for 30 minutes each month burns about 1,913 liters of diesel fuel and emits 57.7 kg of pollutants per year. In contrast, performing the same monthly exercise unloaded consumes less than 1,065 liters per year and total pollutant emissions are reduced by 40% on a kilograms per year basis. Considering one additional scenario, this same generator exercised at no load once every 4 months and one time per year at full load will only consume 550 liters of fuel and emit 70% less total pollutants when compared to a monthly loaded exercise. See Figures 4 & 5. There are also collateral on-site savings. Switching the annual load testing method does not violate NFPA110 requirements. The regulation states that exercising of the unit is required to be performed monthly for 30 minutes at either 30% of rated load or at loads to maintain the minimum exhaust gas temperatures set by the manufacturer. 0 NOx CO 10 20 30 40 50 60 70 6 / Benefits of No-Load Exercising for Diesel Generators
Exercise Pollutant Creation (KD3250 60Hz)
Before revising maintenance schedules, consult with your dealer, service provider, or the manufacturer. Depending upon the types of aftertreatments you use, service schedules and capacities may differ. For example, low-temperature operations in the presence of a combined DOC/SCR/DPF emissions control system may run the risk of oxidizing stored hydrocarbons and damaging the SCR catalyst when exhaust temperatures are later raised through higher loading or could plug the DPF. Regional/local air emissions may also dictate the exercising requirements when using aftertreatment devices. Be sure to consider this during submissions for permitting of the facility. Manufacturers and their channel partners can help you choose the right aftertreatment technologies and match testing loads to permitted levels.
About The Author Justin Loritz, Product Manager–Large Diesel Generators, has more than 16 years of experience with Rehlko in various roles within the organization. After graduating from Michigan Technological University with a B.S. in mechanical engineering, he began his career supporting the large diesel assembly HC PM
Total Emissions
Monthly Loaded Monthly No Load Every Four Months No Load
team as process engineer and progressed through a variety of roles, including lead design engineer for the Rehlko diesel marine product line, production manager
46 | Summer 2026 POWERLINE
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